Stefan Harmansa

Mechanical control of epithelial morphogenesis by the basement membrane

Growing tissues must accommodate forces generated by their own growth while interacting mechanically with their extracellular matrix. How these forces are transmitted and locally interpreted to shape tissues remains a central question in developmental biology.

We use the Drosophila wing disc to investigate how growth, material properties and mechanical coupling drive epithelial organ morphogenesis. The wing disc consists of two mechanically coupled epithelial layers surrounded by a basement membrane (BM). We find that growth incompatibility between the epithelium and BM generates organ-scale stresses that drive morphogenesis. Planar epithelial growth constrained by limited BM expansion produces tissue compression and organ-scale bending, which generates tensile stresses in the overlaying cell layer that drive spatially patterned epithelial shape transitions. Notably, we find that the cellular response depends on regional BM properties: a more compliant BM in the centre permits epithelial flattening, whereas a thicker and stiffer peripheral BM resists deformation and maintains columnar architecture. Mechanical coupling between the epithelial layers further redistributes these stresses through selective shearing.

Together, our findings reveal how differential growth, spatial variation in material properties and mechanical coupling transform local growth into an organ-scale stress landscape that coordinates epithelial organ architecture.